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On a New Method of Preparing a Dissected Model op 

 an Insect's Brain from Microscopic Sections. 



By E. T. Newton, F.G.S. 

 (Read January 2-1, 1879.) 



The structure of the nervous centres of Invertebrate Animals is a 

 subject which is attracting some attention at the present time, and 

 I have myself been much interested in the study of the Insect's 

 Brain ; but have found some difficulty in clearly compreliending the 

 forms of certain of the internal parts. In order to get a better 

 knowledge of these forms, I was led to construct a model, on a 

 principle which I believe to be entirely new. Knowing the interest 

 which our honoured president and the members of this Club always 

 take in new methods of working, I felt constrained to bring the 

 matter before you, and it is the purpose of the present paper to 

 describe the manner in which this model has been constructed. 

 Whether the method will prove available for other objects, time alone 

 will show. 



It will, perhaps, be desirable, before commencing the description, 

 for us to call to mind the general form of an insect's brain. Some 

 of us endeavoured on our last " Gossip niglit" to get a general 

 knowledge of the anatomy of an insect, and, with regard to the 

 nervous system, we noticed, that the most anterior pair of ganglia, 

 which is placed in the fore part of the head, is joined by two large 

 commissures to the second pair, which is placed lower clown, and 

 towards the back part of the head. Through the ring thus formed 

 the gullet, or oesophagus passes, and hence the anterior ganglia, 

 being above, are termed the supra-cesophageal ganglia, and the second 

 being below, are called the inJra-cesopJwgeal ganglia. The positions 

 of these parts is very well shown in the diagram of these ganglia, 

 taken from a Mole-cricket (Fig. 1). The upper ganglia present two 

 rounded prominences above, from the sides of which the optic nerves 

 are given off (op), while at the top are seen two ocelli. Somewhat 

 lower down, and towards the front, are two other prominences, from 

 which the autennary nerves pass off (an). A little lower down a 

 nerve is given off from each side, the two joining in the middle line 

 to form the frontal ganglion [f g.) ; from this a single nerve passes 



